From: Marcelo Tosatti Date: Fri, 18 Sep 2009 23:08:03 +0000 (-0300) Subject: KVM: MMU: fix missing locking in alloc_mmu_pages X-Git-Tag: v2.6.30.9~23 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=005270f475352a33f852cbfb9f49945d7953ea61;p=thirdparty%2Fkernel%2Fstable.git KVM: MMU: fix missing locking in alloc_mmu_pages (cherry picked from commit 6a1ac77110ee3e8d8dfdef8442f3b30b3d83e6a2) n_requested_mmu_pages/n_free_mmu_pages are used by kvm_mmu_change_mmu_pages to calculate the number of pages to zap. alloc_mmu_pages, called from the vcpu initialization path, modifies this variables without proper locking, which can result in a negative value in kvm_mmu_change_mmu_pages (say, with cpu hotplug). Signed-off-by: Marcelo Tosatti Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index a1c5e34e15fda..b70e0ad1094a6 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2692,12 +2692,14 @@ static int alloc_mmu_pages(struct kvm_vcpu *vcpu) ASSERT(vcpu); + spin_lock(&vcpu->kvm->mmu_lock); if (vcpu->kvm->arch.n_requested_mmu_pages) vcpu->kvm->arch.n_free_mmu_pages = vcpu->kvm->arch.n_requested_mmu_pages; else vcpu->kvm->arch.n_free_mmu_pages = vcpu->kvm->arch.n_alloc_mmu_pages; + spin_unlock(&vcpu->kvm->mmu_lock); /* * When emulating 32-bit mode, cr3 is only 32 bits even on x86_64. * Therefore we need to allocate shadow page tables in the first